Iphone Trade-in

If you've upgraded via a cell service provider, you will receive monthly credits towards your bill to the amount of the credit spread over a 24 month period. However if you traded in your phone directly through apple, you will receive an Apple Store Gift Card.

If you paid by credit card, the amount of the trade in goes on the credit card.

If you buy an iPhone, iPad, Mac, or Apple Watch and pay in full, we’ll apply a credit to your original payment method up to the total purchase price. For any remaining amount, you’ll receive an Apple Store Gift Card via email.

If you buy an iPhone using Apple iPhone Payments and include a trade-in, your estimated trade-in credit will be applied directly to the purchase price of your new iPhone. Once we receive your trade-in device and confirm that the condition matches what you described, there’s nothing more you need to do. If it doesn’t match, your original payment method will be charged the difference in value. In that case, we’ll work with you to confirm that you still want to move forward with the trade-in.

https://www.apple.com/shop/trade-in?afid=p238%7Cs0zC2ff4f-dt_mtid_1870765e38482_pcrid_382066772864_pgrid_80259604234_&cid=aos-us-kwgo-brand--slid---apple+trade+in+program-e-product-

If you did purchase is through a cell service provider, they do not give you the full credit directly so that they can protect themselves. That way incase you decide to cancel your plan, they will not have provided you with the full credit and also taken a loss on the phone (even though they would black list the IMEI). Most likely a part of the credit will be given to you each month on your bill. But incase you don't have any of the main cell providers (AT&T, Tmobile, etc), I'd check with them to see what their trade in policy was.